Pope Francis on Friday urged Koreans to pray and work for the re-unification of their divided peninsula, saying they should aim to reunite as one family "with no victors or vanquished."

The pope, in his most specific comments on the division of Korea since he started his five-day trip to the South on Thursday, made the impromptu comments in response to a question by a girl at a youth rally.

"Let us pray for our brothers in the north," the pope said, leading the young people in prayer.

"Lord, we are one family. Help us reach unity. You can do it. So that there are no victors or vanquished. Just one family, only brothers," he said, deviating from his prepared text.

The 1950-1953 Korean war ended in an armed truce that continues, leaving North Korea and South Korea in a technical state of war.

"You are brothers who speak the same language ... think of your brothers in the north. They speak the same language and when in a family the same language is spoken there is a human hope," he said, urging them to "not despair."